HABIT FORMATION IN FROGS 311 



cage engaged the attention of all the four frogs simultaneously, 

 the observations will be presented in exactly the order in which 

 they were made and recorded. 



OBSERVATIONS 



July 26. — Two hairy caterpillars about 2 cm. long (of unde- 

 temiined species) were placed into the cage with the frogs 

 They were eaten, but unfortunately my notes do not state 

 which frogs ate them. The omission does not materially affect 

 the conclusion to be drawn later. 



July 29. — I placed 30 of the hair}" caterpillars into the cage. 

 The caterpillars crawled over everything in the cage. The 

 following is an account of the behavior of each frog toward the 

 caterpillars. The observations lasted about two hours. 



Rana sylvatica attempted to eat a caterpillar seven different 

 times within an hour, but rejected it each time. Following 

 these trials no other caterpillars were visibly reacted to. By 

 attempting to eat a caterpillar and then rejecting it, is meant 

 this : The frog shot out the tongue in the normal manner, 

 bringing the caterpillar back to the mouth, then extruding 

 the tongue slowly, slightly wriggling it. In most cases this 

 muscular wriggling freed the caterpillar from the tongue; if it 

 did not, the withdrawal of the tongue into the mouth scraped 

 oft' the cateqDillar in nearly every case. Sometimes the tongue 

 was wriggled without a pre\ious withdrawal into the frog's 

 mouth. 



Rana clamata (medium) made only two trials of the cater- 

 pillars, rejecting both, and then ceased to react toward them 

 for a while. The frog then jumped into the dish of water. 

 Subsequently a cateqiillar crawled along the rim of the dish 

 opposite the frog. The frog walked over to within 3 cm. of 

 the caterpillar, and paid close attention to its movements for 

 about 15 seconds. Then the frog w^alked backwards about 

 8 cm. resuming the original somewhat indifferent attitude. 

 No further reactions towTird the caterpillars w^ere observed, 

 although they crawied in most tempting situations. 



pMna virescens made three trials of the caterpillars, rejecting 

 every one. No other response to the caterpillars was observed. 



July 30, II A. M. — I colored six caterpillars by sprinkling 

 carmine powder on them, and six others by sprinkling with 



